Surface plasmon resonance (SPR) has been widely adopted as the promising label-free technique in the area of chemical and biological sensing (Chemical Reviews, 108, 462-493, 2008; Analytica Chimica Acta, 620, 8-26, 2008). It offers the potential to replace the conventional laborious florescence labeling approach for biosensing. In addition, SPR biosensors provide real-time quantitative analysis of bio-molecular interactions through monitoring the optical response in terms of (1) angular reflectivity, (2) spectral characteristics or (3) corresponding phase shift.
U.S. patent application Ser. No. 13/113,837 discloses a wide-dynamic-range phase-sensitive SPR sensor based on the combination of spectral and phase investigation via a differential Michelson spectral interferometer. In this application, a dual-path Michelson interferometer is used to introduce sufficient optical path different (OPD) between the probe and reference paths so that spectral interferogram in terms of sinusoidal fringes can be captured to analyze the SPR phase change between the p- and s-polarized beams. While only the phase change in the p-polarized beam is associated with SPR, the phase change in the s-polarized beam is used as the baseline reference.
However, the Michelson configuration is inherently complicated and requires a dummy SPR prism to be placed in the reference path for dispersion compensation.